I imagine that the fines will have to be figured out should the lawsuit succeed. BP, of course, has been stating spill volumes as low as they could, from the start.

Newly released internal documents show the oil giant BP estimates its Gulf of Mexico oil spill could top 100,000 barrels or over four million gallons of oil per day. The number far exceeds the government’s worst-case estimate of 2.5 million gallons, or 60,000 barrels a day. It’s also 100 times the spill rate BP initially claimed and twenty-times what it later told Congress. [Democracy Now, Documents: BP Privately Estimates Spill of 100,000 Barrels a Day, 6/21/2010]

They also released rather poor videos of the leak when (as recently came out) they had a high-definition webcam operating also. This made it difficult for scientists to evaluate how much oil was actually being released.